In the prior art, the labelling of these containers is done by means of special labelling machines, which are usually located in line with machines for forming and subsequently filling and closing the containers, in a single production plant going by the name of Form, Fill and Seal (FFS).
In particular, the containers are generally formed by a heat-forming process, or a drawing of a single sheet of plastic material, such as to obtain an ordered group of containers, all joined together. After forming the group of containers is transferred first to a filler machine, where the container cups are filled with the product, and then on to a sealing machine, where the cups are closed with a film or a suitable lid. Finally, the filled and sealed containers are supplied to a separating machine, where blade cutter devices score and/or cut the flat edges of the container such as to separate them from one another.
Along this production plant, the labelling machine can be located upstream of the filling machine; however, it is generally located downstream of the filler machine, such as to operate with already-full containers of the product to be packed.
Normally, a labelling machine comprises transport means for moving the group of containers through two successive and distinct operating stations, of which a first station in which the heat-shrinkable annular labels are inserted from the bottom onto the body of the containers, and a second heat-shrinking station where the previously-inserted labels are heated such as to cause them to shrink and thus make them adhere perfectly to the containers.
Owing to the presence of these two distinct operating stations, the above-mentioned labelling machine has however a rather limited productivity, and further requires the installation of special mobile support organs which prevent the annular labels from slipping off during the transfer of the containers from the first station to the second heat-shrinking station, thus increasing the level of complication and the costs of construction.
To obviate this drawback, labelling machines have been provided in which the first station is provided with special means for dispensing a hot fluid, typical hot air, which generate jets of the hot fluid which strike the labels immediately after they have been inserted on the relative containers.
In particular, these dispensing means are conformed such that the jets of hot fluid cause localised heat-shrinkage of the labels only at some small portions located immediately below the edge of the relative container, such that these portions adhere to the container itself.
In this way the localised heat-shrinkage effectively prevents the labels from slipping during the transfer thereof towards the following heat-shrinking station, where the true and proper stage of heat-shrinking is done.
One of these machines is described in International application (PCT) no. WO 2005/082601 in the name of Hassia, to which reference is made for further details.
The above-delineated solution, then, obviates the need to provide the labelling machines with means for supporting the labels during transfer, but does not resolve the problems of productivity connected to the presence of two distinct operating stations.
The problems are mostly due to the fact that the two stations need different times in order to complete the relative operations, thus limiting the production rhythm of the whole machine to that of the slower machine, and at the same time requiring the use of complicated and expensive technical solutions for synchronising the two stations to one another.
Also known are labelling machines in which the stages of inserting and heat-shrinking the labels are performed in a single operating station.
The labelling machines are provided with a plurality of label-bearing groups, each of which generally comprises a cylindrical beaker which contains, coaxially to an inside thereof, a respective heat-shrinkable label in the form of an annular band.
The label-bearing groups are associated to means for activating which move the groups cyclically between a loading position, in which they receive a label internally of the relative cylindrical cup, and an unloading position in which they locate the label below a container to be labelled.
Each label-bearing group is further associated to means for raising the relative cylindrical beaker, such as to be able to insert the heat-shrinkable label from the bottom onto the container to be labelled, closing it in the hollow space which is defined between the internal wall of the cylindrical beaker and the external wall of the container to be labelled.
Lastly, each label-bearing group is provided with special dispensing means of a hot fluid, typically hot air, which means dispense the hot fluid internally of the mentioned hollow space between the cylindrical body and the container to be labelled, such as to cause complete heat-shrinkage and thus complete adhesion of the annular label on the body of the container.
One of the labelling machines is described in International patent application (PCT) number WO 2004/085263, in the name of Ghini Enrico, to which reference is made for further details.
These labelling machines are not, however, free of drawbacks.
The positioning of the heat-shrinkable label internally of the cylindrical beaker of the label-bearing groups is for example a difficult and complicated operation, as it is necessary for the label to be perfectly coaxial with the beaker in order not to interfere with the container to be labelled during raising.
Automation of this operation thus requires using constructional solutions which are complicated and sophisticated devices which altogether add significantly to the costs of the labelling machine.
A second drawback derives from the fact that the hot-air fluid dispensing means are directly associated with the label-bearing groups.
This aspect adds to the manufacturing costs of the machine and especially considerably complicates the hydraulic plant supplying the hot fluid, as it has to enable the dispensing means to displace together with the relative groups during transfer of the labels from the loading position to the unloading position.
A third drawback of these machines consists in the fact that the cylindrical beakers of the label-bearing groups can effectively contain a single label format, making the labelling machine poorly flexible and poorly suitable for operating with containers of different sizes.
The aim of the present invention is to obviate the above-mentioned drawbacks in the prior art, with a simple, rational and relatively inexpensive solution.
The aim is attained by a labelling machine and a labelling method, the characteristics of which are respectively recited in the independent claims. The dependent claims delineate preferred and/or particularly advantageous solutions of the invention.
In general a machine is provided for labelling containers, which comprises first transport means for positioning at least a container at a time in a labelling position, second transport means for positioning a heat-shrinkable label in the shape of an annular band below the at least a container in a labelling position, raising means for raising the label in order to insert it from the bottom on the container into a labelling position, and dispensing means of a hot fluid for investing the label with hot fluid, for example hot air or heated steam.
In a first aspect of the invention, the dispensing means are free of the second transport means of the heat-shrinkable labels, such that they are stationary with respect to the labels which advance, moved by the second transport means, and are configured such as to perform heat-shrinking of at least a portion of the heat-shrinkable label inserted on the at least a container which is in the labelling position, which portion extends over the whole axial development of the heat-shrinkable label.
In this way, the labelling machine is effectively able to perform insertion and complete heat-shrinking of the labels in a single operating station, i.e. when the containers are in the above-mentioned labelling position, thus resolving the problems of productivity and synchronisation which are typical of machines having two operating stations.
At the same time the labelling machine is provided with single hot-fluid dispensing means, which operate with all the labels as the labels are positioned below a corresponding container to be labelled, thus contributing to a reduction in costs and constructional complication of the machine.
The hot-air fluid dispensing means are preferably mobile in a vertical direction with respect to the container in the labelling position, between a lowered position and a raised position, and dispense the hot fluid during a vertical displacement between the two extreme positions. In particular, the dispensing means can dispense the hot fluid against the heat-shrinkable label during a displacement from above in a downwards direction and/or during a displacement from below upwards.
In this way the hot fluid dispensed by the dispensing means can effectively strike the label inserted on the container to be labelled over the whole axial development thereof, obtaining complete heat-retraction and perfect adhesion thereof on the container.
The dispensing means are preferably destined to dispense hot fluid jets at a flow-rate and/or velocity which are different according to the axial position of the point of the label which the jets strike. For example, the dispensing means can vary the flow-rate and/or velocity of the hot-fluid jets during the vertical displacement thereof with respect to the container in a labelling position, or can comprise a plurality of outlet nozzles, directed towards a same container in a labelling position and arranged distanced in a vertical direction, which dispense jets of hot fluid having different flow-rates and/or velocities.
In this way, the labelling machine can obtain an effective heat-shrinkage of the labels, even when the containers to be labelled have a generally flared shape, for example truncoconical.
The dispensing means preferably comprise a plurality of diffuser elements which are distinct and reciprocally separate, which are arranged such as to define a ring-fence that surrounds the at least a container in a labelling position, and which are singly provided with at least a nozzle for exit of the hot fluid directed towards the inside of the fence, such as to invest the label inserted on the container in a labelling position with the hot fluid.
Thanks to this solution, each label inserted on a container in a labelling position is struck by the hot-air fluid jets coming from different directions, which can thus strike a whole annular strip of the label, with the result that the heat shrinkage is particularly complete and effective.
The second transport means for positioning the labels below the containers to be labelled preferably comprise a plurality of label-bearing groups which are singly destined to transport a label which is coaxially inserted thereon, and means for drawing for moving the label-bearing groups between a loading position, in which they receive the label, and an unloading position in which they locate the label below a container in a labelling position. The label-raising means are separate from the second transport means, such as to be stationary with respect to the labels which move between the loading position and the unloading position, and comprise at least a vertically-mobile pusher, which pushes the label located in the unloading position from the bottom such as to raise it, freeing it from the label-bearing group and introducing it on the container in the labelling position.
A second aspect of the invention relates to a loading device for inserting the labels on the above-mentioned object-bearing groups in a loading position. The loading device comprises a shaping element having an axial development aligned with the label-bearing group in the loading position, and at least three drawing organs arranged in succession along the axial development of the forming element, which are associated to respective activating motors for drawing and making a tubular body run independently, the tubular body being made of a heat-shrinkable material and being inserted on the forming element towards the label-bearing group in the loading position. In particular, the last of the drawing organs draws the tubular body at a faster velocity than the other drawing organs, such as to separate an annular length of heat-shrinkable material from the end of the tubular body and to make it slide on the forming organ up until it is inserted on the label-bearing group in the loading position.
Differently to the prior art, which generally includes the forming element being associated to two only of the drawing organs, which impress different velocities on the tubular body in order to tear off the end piece thereof, the solution of the present invention enables greater control over the sliding of the heat-shrinkable tubular body over the forming element, effectively preventing pulls and/or tears in undesired points, which might compromise correct functioning of the whole labelling machine.